Antigenic Protein Screening and Design of Multi‐Epitope Vaccine Against <i>Lactococcus garvieri</i> and <i>Streptococcus iniae</i> for Combating <i>Lactococcosis</i> and <i>Streptococcosis</i> in Fish

The illness caused by Lactococcus garvieae and Streptococcus iniae is well acknowledged as a disease that results in significant economic losses since it affects a diverse array of fish species. The constraints of existing vaccinations and techniques have prompted the exploration of novel approaches to manage this ailment. Multi-epitope vaccines that use a diverse range of immunogenic proteins have considerable potential. The primary objective of the present research endeavour was to develop a very effective multi-epitope vaccine targeting Streptococcus iniae and Lactococcus garvieae infection in fish. The immunogenic components of Lactococcus garvieae and Streptococcus iniae were used for epitope prediction. A multi-epitope vaccine was constructed using the immunogenic proteins' most effective B cell epitopes and the GFFY adjuvant. Subsequently, an assessment was conducted on many aspects of the developed vaccine, including physicochemical characteristics, antigenicity, secondary structure and tertiary structure. Furthermore, the molecular docking technique was used to study the interaction between the proposed vaccine and its TLR-5 receptor. The nucleotide sequence of the vaccine was subsequently modified to facilitate its expression in Lactococcus lactis. The findings of the current investigation indicate that the vaccine developed exhibited stability, as shown by its molecular weight of 93989.19 Da and antigenicity value of 0.8547. In addition, the study of the vaccine's structure indicated that it consisted of 32.24% alpha helix, with 88.41% of its residues located in the preferred area. The proposed vaccine effectively docked to its TLR5 receptor was shown, resulting in the lowest energy of -995.4. According to the data obtained, the developed vaccine has the potential to effectively prevent infection in fish caused by Lactococcus garvieae and Streptococcus iniae. Our findings suggest that the peptide vaccine might be a favourable choice for prophylaxis against Lactococcus garvieae and Streptococcus iniae.